Suppression of Brown spot in upland rice by beneficial bacteria.

Diseases caused by Bipolaris oryzae (Bo) affect rice (Oryza sativa) productivity and reduce producer rentability. The objective was to select antagonistic isolates to B. oryzae. The first trial was carried out in a completely randomized experimental design (DIC), with 10 treatments (9 bacterial isolates 11 F, 15 F, 32 F, 33 F, 114 F, 182 F, 187 F, BRM 63521 and BRM 63522 and a control), 5 replications, under laboratory conditions. The pathogen and bacterial isolates were cultivated as dual culture, in Petri plates containing PDA. The second trial, under greenhouse conditions, tested two application modes of bacterial suspensions and two rice cultivars. The application methods were by microbiolozation and spraying the leaves with a suspension of bacteria (10 8 cfu.mL-1 ). Seeds of cultivars BRS Primavera and BRS Esmeralda were sown in plastic trays containing 3 kg of fertilized soil, and 45 days after planting, the plants were sprayed with a suspension of Bo conidia (1x105 con.mL-1 ). The isolates BRM 63521 and BRM 63522, alone or in combination were antagonists to Bo. The two isolates, BRM 63521 and BRM 63522 were identified as Serratia marcescens and Serratia nematodiphila, and the combination between them were efficient in reducing the severity of brown spot in both rice plants cultivars, on average 93.2% and 64.9%, for microbiolization and foliar spraying methods, respectively. In addition, both isolates reduced the number of conidia produced by each lesion. The isolates are promising for the control of brown spot in rice.